What is split stone?
Split stone is a collective term for stone that is split rather than sawn. The Dutch term splijtsteen has two meanings: natural stone that can be split into slabs because of its layered structure, and fired clay units that are split in two after firing. Do not confuse it with a split brick, which is a brick that delaminates because of a production or frost defect.
Two types
1. Splittable natural stone. Some rocks have a natural bedding or cleavage along which they break into slabs. Well-known examples:
- Slate. A metamorphic rock formed from claystone or shale under pressure and heat. Split slate has a naturally rough surface and is never exactly the same thickness throughout.
- Quartzite. Also metamorphic: sandstone that has recrystallised under high pressure and temperature, without melting. Splittable quartzite is hard and very wear-resistant.
- Bedded sandstone and limestone. These are true sedimentary rocks; some types split along their bedding planes and are sold as flagstones.
2. Fired split units. Clay is extruded as a double unit, dried, fired and sometimes glazed. It is then split in two, giving two thin units with a normal brick face. These are used as brick slips, as a thin facing layer or in prefabricated facade panels.
Application
- Allow for thickness variation. Split natural stone varies in thickness. Lay paving in a mortar bed that takes up the difference, or choose calibrated (gauged) slabs.
- Ask about frost resistance. Outdoors, both natural stone and fired units must be frost-resistant. Ask for the manufacturer’s declaration of performance.
- Brick slips: follow the system. Fix brick slips according to the system supplier’s instructions, including substrate, adhesive and pointing mortar.
- Respect the bed. Bedded sandstone or limestone belongs on its natural bed in a wall: layers horizontal. If the layers are parallel to the wall face, frost can make them peel off in sheets.
Common mistake: laying uncalibrated split slabs on a thin bed of adhesive. The variation in thickness leaves voids, so slabs can crack or come loose.
Related terms
- Slate
- Quartzite
- Metamorphic rock
- Sedimentary rock
- Split tile
- Extrusion
- Brick manufacturing
- Facade cladding
Want to know more about building terms? Visit our knowledge base at fredsdiyplans.com.